His research is based on phonemes, distinct units of sound such as vowels, consonants and tones, and an idea borrowed from population genetics known as “the founder effect.” That principle holds that when a very small number of individuals break off from a larger population, there is a gradual loss of genetic variation and complexity in the breakaway group.

Dr. Atkinson figured that if a similar founder effect could be discerned in phonemes, it would support the idea that modern verbal communication originated on that continent and only then expanded elsewhere.

In an analysis of 504 world languages, Dr. Atkinson found that, on average, dialects with the most phonemes are spoken in Africa, while those with the fewest phonemes are spoken in South America and on tropical islands in the Pacific.

The study also found that the pattern of phoneme usage globally mirrors the pattern of human genetic diversity, which also declined as modern humans set up colonies elsewhere. Today, areas such as sub-Saharan Africa that have hosted human life for millennia still use far more phonemes in their languages than more recently colonized regions do.